1. Field of the Invention
The present invention relates, in general, to computer systems and mass data storage systems and subsystems, and more particularly, to a position sensing system and method for use in automatically and passively determining physical locations of device or other enclosures within data storage system racks or cabinets having multiple shelves or enclosures.
2. Relevant Background
In the computer industry, there is ongoing and increasing demand for data storage systems with more capacity as well as improved reliability. The use of RAID (Redundant Arrays of Inexpensive Disks) systems has significantly enhanced data storage reliability by providing redundancy, i.e., failure of one system component does not cause loss of data or failure of the entire system. Although initially RAID systems generally provided redundant disk drives, more functional redundancy has recently been provided by extending redundancy to device enclosures. These enclosures may include a number of components such as power supplies, cooling modules, disk devices, temperature sensors, audible and/or visible alarms, and RAID and other controllers. To provide functional redundancy, the enclosure typically includes an extra one of each of these components that is needed for proper functionality. For example, two power supply units may be provided such that if one fails the remaining power supply unit is capable of providing adequate power.
A data storage system, e.g., an enterprise data center or complex, includes numerous multi-shelf cabinets or racks each holding multiple enclosures. The system is adapted for replacement of individual enclosures to upgrade or modify the system or in some cases, to service an enclosure. If an enclosure no longer has functional redundancy, e.g., one of its power supplies has failed, a system administrator will replace the entire enclosure or the failed power supply. To facilitate replacing or otherwise servicing enclosures, it is necessary to first identify the physical location and operating status of each enclosure within each cabinet and more specifically, to view the location and status of each enclosure on a monitor and/or graphical user interface (GUI).
Previously, the physical locations of components, such as enclosures, in data storage systems have been entered into databases used by monitoring software to display the location to the system administrator on the GUI. However, the manual entry process is susceptible to human error in initially entering the data and in updating the location information as the system is modified and grows in number of cabinets and enclosures in each cabinet. If the location is incorrect, the administrator most likely will remove and replace the wrong enclosure. Efforts to use analog sampling and polling have resulted in improved position detection within systems but have not been without problems due to noise, linking to fibre channel loop addressing, and added software monitoring complexity.
Hence, there remains a need for an improved method and apparatus for identifying the physical location of each enclosure in a data storage system. Preferably, such a system would support field replacement of individual enclosures, would not interfere or reduce data transfer or other functionality of the enclosures or included components, and would provide enclosure, shelf, and cabinet identification information for each enclosure within a system independent of its address on a fibre channel loop.